The recent availability of optical frequency-combs has made possible, for the first time, direct optical frequency measurements. This, in turn, opened the way to atomic clocks based on optical transitions which could be superior in accuracy and in stability compared with the actual microwave atomic standards. Among all possible atomic sources, a sample of neutral Sr atoms has been considered as one of the most interesting candidates because of the simple level scheme which presents a set of transitions well suited for laser cooling down to almost quantum degeneracy, as well as narrow linewidth clock-transitions (linewidth <1mHz for the fermionic ⁸⁷Sr isotope). We intend to define a new frequency standard, referenced on visible transitions of atomic strontium.

Atom interferometry gravity-gradiometer for the determination of the Newtonian gravitational constant G

The goal of MAGIA experiment is the high precision measurement of the Newtonian Gravitational Constant G using atom interferometry.

More than 300 measurements have been done, but there are only a few methods which can be considered conceptually different: torsion balance, torsion pendulum, beam balance and pendulum cavity.

All these methods have in common that masses, which probe the acceleration caused by well known source masses, are suspended, for instance with fibers. This possible source of systematic effects can be eliminated if one performs a free-falling experiment.

Free falling Rb atoms will be used as probe masses to test the gravitational acceleration of nearby source masses. The combination of Raman atom interferometry and laser cooling will allow us to achieve high sensitivity. Using atoms with well known properties, instead of macroscopic probe masses, will help to reduce systematic errors and permit an accuracy at the level of 10^-4.

Coherent matter-wave optics is still a very young field, far less developed and more complex than conventional optics for light. This field represents an emerging area of science, quantum engineering, with a high potential for a future technology and multidisciplinary applications.

Thanks to an impressive evolution and remarkable inventions, the ultimate potential of matter-wave sensors is entirely open. For the closely related field of atomic clocks, the growth in performance was exponential during the last decades! This is the reason why matter-wave sensors are considered as one of the most promising fields to progress in metrology and fundamental tests. On the other hand, it is still an open question, if quantum engineering will once become a technology with major applications (beyond clocks) in every day life. Inertial quantum sensors provide a new tool for the precise detection of faint forces and tiny rotations. According to the principle of these sensors, the measured physical quantity will be converted into a frequency, which can be measured with highest accuracy (nowadays, time and frequency standards are the most precise standards).

The outstanding feature of these sensors is the precisely known scaling factor: there is no need for calibration, which predestines these sensors for inertial references and for applications for the Système International.